The present invention relates to compositions and methods of use for the dispersion of contaminants during the recycling of coated papers. Wax is considered a contaminant, and the dispersability of wax is a critical component in the viability of recycling methods for wax coated fibers.
Old corrugated containers (OCC) make up a high percentage of the recycled paper used in the United States, a majority of which is made into new container board. With such a high reuse level, old corrugated containers are an extremely important raw material for the container board industry. A potential significant source of OCC are wax treated containers. Wax treated containers are corrugated containers which are coated or impregnated with wax and used to ship fruit, produce and other agricultural products, as well as nonagricultural products such as bulk nail, screw, and bearing boxes. Wax treated containers represent an attractive fiber source due to their plenitude as well as the fact that one type of wax treated containers, namely, waxed corrugated, is typically produced from virgin fiber; making used waxed corrugated containers a high quality fiber source.
Currently, waxed corrugated is not accepted for recycling because it is considered too contaminated. If an attempt is made to recycle waxed corrugated, it fails because during the recycling process, released wax tends to collect on equipment and in the finished paper products causing problems with mill operations and affecting product quality. To reasonably increase the level of waxed OCC used by the paper industry to the point where mills will accept and possibly seek out waxed containers, significant improvements in new technology for controlling wax in the recycle plant will have to be made.
Approaches in the recycling industry for dealing with wax contamination have been threefold. The first solution is: repulping of the recycled wax treated containers with improved mechanical processes to aid separation. The second solution is using coating additives during application of the initial wax coating of the paper. The third solution is using repulping additives to improve the repulping process.
Mechanical improvements to the recycling process to increase efficiency (the first type of solution to the problem) include the use of ultrasound as described in U.S. Pat. No. 4,045,243 and a high pressure stream of steam in U.S. Pat. No. 4,312,701.
Development of more readily repulpable coatings (the second type of solution to the a problem) that can be easily separated from fiber and removed with conventional cleaning systems (i.e., screens and cleaners) is ongoing. For example, dispersant coating additives are generally described in Patent Cooperation Treaty Patent Application WO 91/05107. Many polymeric additives to coatings have also been identified such as copolymers of acrylamide/acrylic esters; disclosed in U.S. Pat. No. 3,262,838. Additional polymeric additives to coatings include the copolymerization product of styrene and the half ester formed by the half esterification of one mole of an alpha-beta unsaturated dicarboxylic acid, disclosed in U.S. Pat. No. 3,287,149; butadiene-methyl methacrylate copolymer latex, disclosed in U.S. Pat. No. 4,117,199; a wax composition, disclosed in U.S. Pat. No. 5,539,035 and a variety of other polymeric coating additives, disclosed in U.S. Pat. Nos. 5,491,190; 5,658,971 and 5,654,039.
Another coatings additive useful in the creation of repulpable coatings are more readily repulpable hot melt adhesives, disclosed in U.S. Pat. No. 5,541,246.
Examples of the third type of solution (the development of repulping process additives) are a hydrophobically modified associative polymer including hydrophobically substituted polyethylene oxide polymers, disclosed in EP 0,568,229 A1; a substituted oxyethylene glycol non-ionic surfactant and a water-soluble low molecular weight polyelectrolyte dispersant, disclosed in U.S. Pat. No. 4,643,800; alkylamine polyethers for foam control, disclosed in U.S. Pat. No. 4,483,741 and use of trisodium phosphate, disclosed in U.S. Pat. No. 1,628,931. Moreover, additives to the repulping process for the removal of ink include long-chain akcohols, disclosed in U.S. Pat. No. 5,500,082 and surface-active poly(ethers), disclosed in U.S. Pat. No. 4,518,459.
What are needed are additional contaminant dispersant compositions capable of dispersing wax and other contaminants so that wax coated fiber can be effectively recycled.
The first aspect of the invention is a method of dispersing contaminants in a fiber slurry comprising the steps of:
A.) optionally mixing the slurry;
B.) adding to the slurry, while optionally mixing the slurry, a contaminant dispersant comprising
1) a plasticizer, and optionally
2) one or more ingredients selected from the group consisting of
a) an anionic dispersant in combination with water containing either:
i) acid or lecithin and; optionally a base; or
ii) a preneutralized component; and
b) a surfactant wetting agent optionally in combination with water containing either:
i) acid or lecithin and optionally a base; or
ii) a preneutralized component;
wherein if said plasticizer is the only ingredient present, said plasticizer is 2,2,4-trimethyl-1,3 pentanediol duisobutyrate; and
C.) mixing said fiber slurry and allowing said contaminant dispersant to disperse contaminants present in said fiber slurry, causing formation of uncontaminated fibers.
The second aspect of the invention is a contaminant dispersant comprising:
a) water;
b) a plasticizer;
c) an anionic dispersant;
d) a surfactant wetting agent; and
e) either
1) a combination of an acid or lecithin and optionally a base, or
2) a preneutralized component.